The 2016 Florida legislature delayed the building code requirement for residential blower door testing on all new residential construction until July 1, 2017. But now, the requirement is upon us. Permits for new residential construction after July 1st are now going to require this testing be performed, and signed off by your building inspector, prior to final. (Plan for an additional cost between $350-$750 for this test, depending on the size of the home. Don’t forget to add delay cost and additional time to your construction schedule too. If mechanical ventilation is required – budget an additional $500-$1000 per air handler.)
The blower door test will measure the air tightness of the home, expressed in ACH50 (Air Changes per Hour – pressurizing the home at 50 Pascal pressure). Note that the test will delay all other construction inside the home during the test and can last for up to 8 hrs. Homes that are considered “leaky” are considered to have an ACH50 >=7. A home that is “tight” will be considered to have a ACH50 <= 3. Most new homes (conventional wood frame) will have a ACH50 value testing between 3 and 7. Homes testing with 7ACH50 or greater will require additional sealing of cracks and penetrations, and then require a blower door re-test (at additional cost until the test results in ACH50 < 7) Homes testing less than 3ACH50 will require mechanical ventilation be added to the air handler. Fully spray foam insulated homes or insulated concrete homes (with a low window-to-wall ratio and few roof and exterior wall penetrations) are too types of high performance homes that could test out at 3ACH50 or less, and would therefore require mechanical ventilation. Plan ahead. Make sure your energy compliance form provider is experienced with mechanical ventilation. Mechanical ventilation can increase the tonnage requirement for the a/c system and will require special attention with regards to home de-humidification. To consider mechanical ventilation after the fact (that is, after the equipment is sized and installed and the blower test indicates its required) may result in a/c equipment too small to implement afterward. So make sure your energy sheets (calcs) provider understands this ahead of time and can make compensation up front. Also, if there is a real possibility of mechanical ventilation being required, make sure you coordinate with your architect during the design phase to layout a location for the air handler either in the attic, garage, or close to an exterior wall,where mechanical ventilation ductwork to the exterior could be easily routed should it be required as a result of the blower door test results.
Finally, check with your local municipality plan review and inspection departments to further understand what they are going to specifically require regarding the blower door test and mechanical ventilation after July 1st.